Many other artists gradually began making circles of greater and greater complexity. Most notably, a group called 'The Circlemakers' have made various intricate patterns, including a recent portrait of Richard and Judy of UK TV fame.
Is there a crop circle that couldn't have been made overnight by a team of dedicated humans? A member of The Circlemakers, John Lundberg, can only suggest one example - a formation that appeared in Milk Hill in 2001. It had 409 circles and was nearly 300 metres across.
"If this formation was man-made allowing for time to get into and out of the field under cover of darkness the construction time left should be around four hours. Given that there are over 400 circles, some of which span approximately 20m in diameter, that would mean that one of those circles would need to be created every 30 seconds. And that's not even allowing any time for the surveying, purely flattening, this formation pushes the envelope and that's a MASSIVE understatement."
http://www.bbc.co.uk/science/space/l...es/human.shtml